Experimental study and analysis of hydrostatic pressure sensitivity of polymer fibre Bragg gratings

The intrinsic hydrostatic pressure sensitivity of polymer optical fiber Bragg grating (POFBG) with different diameters are investigated. POFBGs are inscribed in single-mode polymer fiber and etched down to different diameters. We have experimentally demonstrated that the material properties of the polymer optical fiber can change after etching and thus the etching procedure can have an impact on the pressure sensitivity of the POFBG. It is observed from the experimental results that hydrostatic pressure induces a positive wavelength shift to the POFBG and the pressure sensitivity of the POFBG shows significant increase as the fiber diameter reduces through etching. A pressure sensitivity of 0.20 pm/kPa is obtained for an unetched POFBG while for an etched POFBG with 55-μm diameter a sensitivity of 0.75 pm/kPa is observed. Temperature compensation techniques are also successfully implemented to extract the true intrinsic pressure sensitivity of the POFBG. Through this study, the intrinsic pressure sensitivity of POFBG with different diameters are obtained and also the significance of etching and its impact on pressure sensitivity is demonstrated. This information can lead to further research and development on high sensitivity pressure transducers based on etched POFBGs.